30.01.2026 by Viktor Siebert
Repair of a Yaskawa AC Servo Motor SGMGV-30ADA61 with Encoder Fault
Initial Condition on Arrival.
The Yaskawa AC Servo Motor SGMGV-30ADA61 was sent to us with a clearly reproducible encoder fault. According to the customer, the error already occurred when the machine was powered on. The axis could no longer be referenced and stable operation was no longer possible. Encoder and position-related errors were displayed in the machine control, which are typical in combination with Yaskawa Sigma V servo drives (SGDV series) when the feedback signal is unstable or incorrect.
Due to an acute production downtime, the customer decided on an express repair with a turnaround time of 48 hours.
Initial Inspection and Diagnosis
After arrival, the motor was first inspected externally. During visual inspection, age-related wear was already visible in the area of the sealing elements. Electrical input measurements of the encoder and motor windings were then performed. The winding values were within specification, but the encoder no longer provided a stable feedback signal.
In the next step, the motor was mechanically disassembled. In the encoder area, we found clear signs of wear as well as early contamination that had entered the housing over time. In addition, the ball bearings already showed rough running characteristics, which would have led to further consequential damage in the long term.
Repair Work Performed
As part of the repair, the motor was completely disassembled and all relevant assemblies were inspected individually. The defective UTTIH-B20FK encoder was fully replaced. During this process, not only the encoder itself was exchanged, but the entire connection area was inspected and newly sealed.
At the same time, we decided to carry out a preventive mechanical overhaul. Both motor bearings were replaced with new high-quality ball bearings. Old sealing elements were completely removed and replaced with new seals to restore long-term protection against dust, moisture, and oil mist.
After reassembly, the encoder was adjusted and a final functional check was carried out.
Test Run and Quality Assurance
The motor was then operated on our Yaskawa test bench and tested with a Sigma V servo drive (SGDV series) under realistic operating conditions. The following aspects were verified:
- stable encoder feedback across the entire speed range
- smooth motor operation without abnormal noise or vibration
- thermal behavior during continuous operation
- clean control response during acceleration and deceleration
The motor ran fault-free for several hours, and no encoder or position alarms occurred. The repair was therefore successfully completed and the motor was returned to the customer within the agreed 48-hour timeframe.
Conclusion
This repair case clearly demonstrates that encoder faults in high-performance servo motors such as the SGMGV-30ADA61 rarely occur in isolation. Aging bearings and hardened seals significantly accelerate secondary damage. By combining encoder replacement with bearing and seal renewal, the motor was not only repaired but restored to a technically sustainable operating condition.
Further information such as price and delivery time for: Yaskawa AC Servo Motor SGMGV-30ADA61
Mentioned Yaskawa Encoder UTTIH-B20FK
More details about our Yaskawa repair expertise can be found here: Yaskawa Servo Motor Repair at Industrypart
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Yaskawa AC Servo Motor SGMGV-30ADA61
Technical Specifications
| Parameter | Value |
|---|
| Manufacturer | Yaskawa Electric |
| Motor Type | AC Servo Motor |
| Model | SGMGV-30ADA61 |
| Rated Output | 2.9 kW |
| Rated Torque | 18.6 Nm |
| Rated Speed | 1500 min⁻¹ |
| Rated Voltage | 200 V |
| Rated Current | 23.8 A |
| Insulation Class | F |
| Duty Type | Continuous duty |
| Encoder | UTTIH-B20FK |
| Origin | Made in Japan |
Operating Environment and Typical Applications
This motor is typically used in CNC machines, machine tools, machining centers, and automated production systems. It is especially common in axis applications with high requirements for positioning accuracy and continuous load capability.
Functional Description
The SGMGV-30ADA61 is a high-performance AC servo motor with high-resolution encoder feedback. In combination with Yaskawa Sigma V servo drives, it enables precise torque, speed, and position control. The encoder provides the essential feedback for the closed-loop control system and is therefore a key component for the overall performance of the drive system.
Typical Encoder-Related Alarms (SGDV Sigma V)
The following alarms frequently occur in connection with encoder faults or encoder cable issues:
| Alarm Code | Description | Possible Cause | Corrective Action |
|---|
| A.80 | Encoder error | Encoder defective | Replace encoder |
| A.81 | Encoder communication error | Cable or encoder | Check cable or replace encoder |
| A.84 | Absolute position error | Encoder initialization failed | Check encoder |
| A.86 | Encoder data error | Signal disturbance | Check connectors |
| A.90 | Position deviation | Implausible feedback | Check encoder |
| A.91 | Encoder timeout | Interruption | Replace cable or encoder |
| A.92 | Encoder power supply error | Voltage issue | Check drive or encoder |
| A.93 | Initialization error | Encoder defective | Replace encoder |
| A.94 | Data inconsistency | Internal encoder fault | Replace encoder |
| A.95 | Communication loss | Cable break | Check wiring |
Motor Components
| Assembly | Description |
|---|
| Encoder | Position feedback unit UTTIH-B20FK |
| Ball Bearings | Mechanical support of the motor shaft |
| Seals | Protection against dust and moisture |
| Windings | Stator windings for torque generation |
| Motor Housing | Mechanical protection and heat dissipation |